ECN Forum Forums Safety Discussion and News Safety News and Product Recalls Burning Wirenut

Greg, that tubing is almost identical to "Smurf tube." It connects to ... nothing! You simply poke it through the hole. No clamp or fitting at all.
I would often find boxes with the tubing protruding excessively into the box, or stopping just short of the box.

The tubing is installed into routed chases in the masonry, and secured by the mortar used to patch the chase. No clips or staples or clamps.

The boxes themselves have extremely weak mounting to the wall. You can often see them move about when you have them open.

Devices typically have ears that expand out, you hope to catch on serrations inside the box. The arrangement is similar to that used on some of our old-work boxes, but not nearly as secure.

As a result, simply 'pulling the plug' frequently results in the box partly pulling out of the wall. "Child art" instructs all that the "proper" way to pull a plug is to first place one hand against the cover-plate, holding the box in place; then you pull the plug with the other hand.

Hot spots occur from only ONE phenomenon

HEAT

Ul determined this almost 40 yrs ago

There exists NO technology to mitigate this distally

~S~

HEAT makes things hot?

I believe you.

The larger question is making assumptions when you are called out to a residence.

My working assumption is that I can't assume anything.

1) Bad original work.

2) Even worse DIY

3) Dufuss hack called out -- before a real electrician... oh, so typical...

4) At absolute wit's end... a REAL electrician is called into action. His talent/skill knowledge base can't be acknowledged -- as that would put him up there with the professionals....

The Big Box Store and the Internet said ANYONE can wire stuff correctly!

Rather descriptive of my 30 yr career Tesla.

Yet while the markets 'hidden hand' rejoices in the glory of diy'er , the bureaucracies brew more and more doctrine they'll never be confronted with , or need care about

Fact is, all those 'alphabet dept oversight' sorts so well known to us rarely make public appearances addressing the proliferation of diyers fueling their safety goals

From a purely objective stance, this can be seen as engineered to come down on and alienate that 'real electrician'

That most of us are left to explain the ever expanding NEC to defend our profession is akin to being it's emissary, liaison, intermediary

This is why i keep it simple....but at the same time don't shill for the predators who've infiltrated it

Heat is the enemy , now go ask what the market has for that, and get back to me

~S~

+ 1 Hotline the cover is an important part, in the example if the cover were metal it likely would have caused the breaker to trip as soon as the plastic melted away, thus eliminating the heat source. Also the cover limits the air supply in the box(duh) and attempts to smother the fire. How many j-boxes have you opened that had charred connections? Twist the joint tight, use a listed connector, and put a cover on it!

Assuming proper grounding, metal contact would mitigate a parallel arc. We have OCPD's of either normal or enhanced (GFCI, GFPE)caliber to mitigate this.

What do we have to mitigate series arcs?

And can anyone point it out in this UL paper

~S~

Having never used a wire-nut before.
Do you guys twist the wires together before the wire-nut is fitted?
One thing I've never liked about wire-nuts, is that they can cut into the wires that they are supposed to be clamping.

A challenger appears:



This device has a metal tunnel that the wires fit into, there is a top metallic tongue that protects the wires from the screws biting into the wires as the 2 screws are tightened.
The outside is insulated to 500VAC.

Trumpy:



I prefer to Pre-Twist the Conductors, prior to applying the Wire Nut.

Oh, BTW, that Terminating Device looks like a Supercharger!!! (Blower / Roots-Blower)

--Scott (EE)

Scott,
Real world pictures.
These things are about an inch long and an inch wide in the domestic sizes.
As they get bigger, the terminal tunnel gets bigger, the next size up has a "tongue" that ensures the wire strands aren't damaged by the 2 screws.
The one shown is made for looping wires at a box.

Just responding to some quesions that came up. Germany doesnt use smurf tube on-wall, the picture is just a demo. The tube usually is plastered into brick/concrete walls or used inside drywalls. Then a NYM cable (our romex equivalent, but round with an insulated ground wire) or single wires are pulled in. It's also possible to directly plaster the NYM in or use it in drywall without a tube.

Also, most of our wall boxes are round. The one shown in the pic is a wet location on-wall box missing the plastic bushings for round NYM cable.

Those spring-loaded connectors are advertised as never coming loose (compared to the ones with screws we used back in time) because the spring compensates the copper's cold flow over the years. Wirenuts are seldom seen.

I have never seen a molten spring connector unless on internet pictures. Usually the cause then is that the wire was not inserted far enough into the spring, or the wire was damaged, corroded etc. The copper has to be straight and round. If the wire is deformed from being used in a screw connector before, you should cut off a bit.
The first ones were gray but most of them are clear now so you can see the proper wire insertion.

The ones Trumpy posted are used in Italy, but I believe they only have one screw there. We had the same ones back in time but open for wires on both sides.